Alkyd resins may be rendered water-reducible by grafting with olefinically unsaturated carboxylic acids, especially alpha-unsaturated carboxylic acids like methacrylic acid or by co-condensation with polycarboxylic acids such as tetrahydrophthalic acid or hydroxycarboxylic acids having acid groups which do not react, or only react to a small extent, under polycondensation conditions by esterification, yet impart hydrophilicity after being neutralised with alkaline compounds to provide a sufficient number of anionic groups in the resin molecules.
Water-reducible alkyd resins where fatty acids bearing grafts derived from acrylic monomers have been known, i. a. from EP 0 267 562 A2, EP 0 295 403 A2, EP 0 437 743 A2, WO 1995/027 762 A1, and WO 2006/092211 A1.
Efficient surface protection, particularly for flexible or deformable substrates such as plastic or wood parts, needs high molar mass resins which provide the needed combination of elasticity, hardness, weathering and chemical resistance. As high molar mass resins exhibit high viscosity in melt or solution, they cannot easily be made as also the reaction rate decreases with increasing viscosity. While the viscosity can be reduced by addition of a solvent, this solvent would have to be removed before or preferably after formation of the resin dispersion.